Determination of rational friction temperature in lengthwise rolling
A. Yu. Albagachiev, A. M. Keropyan, A. A. Gerasimova, О. А. Кобелев, JSC “RPA “CNIITNASH” (Moscow, Russia)
Abstract
The paper presents the study of the process of lengthwise rolling. This process is characterized by elastic-plastic deformation, slipping friction, seizing friction, rest friction arising in the contact area between rolls and strip. The rolling process during the contact between rolls and strip is described, as well as rolling forces causing elastic deformation of metal products. The work of elastic-plastic deformation and friction is the cause of contact heat forming during lengthwise metal rolling. The contact temperature can vary depending on its value from room level (at low energy values and small deformation rates) to high temperature (at high energy values and large deformation rates). Friction during plastic deformation is described by complicated relationship, and it varies from classic friction with its dependence on l/h during rolling and upsetting. If l/h relationship is less than 0.5, seizing area spreads along whole length of curve seizing and tangential friction forces don’t reach the maximal values. If l/h relationship is 0.5–2.0, seizing areas spreads along whole length, while tangential forces reach maximal values in the entrance and exit of a roll area. It is necessary to differ average contact temperature, volumetric and temperature burst owing to discreteness of a contact area. The formulas for temperature calculation in friction conditions, depending on technical conditions, thermal, physical and mechanical properties of materials and contact geometry for parabolic case of variation of friction intensity by time, are concluded in the paper based on solution of Fourier parabolic equation of heat conductivity. The formula for calculation of the contact temperature between a roll and rolled strip is concluded. Recommendations for use of the formulas are given. If we know the optimal and experimentally found rolling temperature (it is individual for each metal), we can solve the backward task, i.e. determine the rolling procedures via presented formulas.